Re: [Visualpython-users] VPython and Pentium 4 HT conflict

[Jonathan B. <jbr...@ea...>]

On Fri, 2004-11-05 at 14:54 -0800, Bruce Peterson wrote:
> Jonathan
>     This will be a rather long message as I am attaching some of our 
> correspondence of mid-August.  The problem was (and still is with the Nov 
> 04 release) that my application using the new VPython will run fine on a 
> standard P4 but when run on a P4 with HT will run for several to a dozen or 
> so iterations before crashing and getting the "send error to MS" window. 
> Reverting to the old (Nov 03) VPython eliminates this problem.
> 
> The conversation ended with (at least in my mind) the problem being some 
> conflict between the Pentium hyper-threading and the Visual Python 
> libraries that hopefully would be resolved with a newer release.
> BTW -- the app (with the Nov 03 VPython libraries) is at 
> www.terastat.com/VisualFilter.htm, as I mentioned it's rather complex -- I 
> can stick a version with the new VPython out on the web if you're interested.

Can you put up a link to a tarball or zip archive of the source?


>  > Well its looking more and more like the problems are due to the HT-P4 and
>  > how it handles VPython. Using the old VPython (oct 2003), I can launch
>  > multiple copies of the client, and the server will create multiple,
>  > synchronized, Vpython displays -- this on a Dell Xeon 2.1 GHZ processor.
>  > When I attempt to do this on the P4-HT notebook -- only the first instance
>  > runs, the second can't find the server.
>  > One on the joys of Python is that I can run my server code as a standalone
>  > application (for testing) with no code changes. When I do this, I can run
>  > two copies on both the Xeon and P4-HT machines.  So it appears that
>  > software threading has problems on the P4-HT -- and the new VPython
>  > aggravates these.
> 
> Since the language binding between Python and C++ was completely
> replaced, some functions are a little slower, and a few functions are a
> pinch faster than before.  This small difference in timing (plus the
> availability of an HT Pentium and a dual-proc PowerMac) exposed several
> latent threading bugs in VPython during development.  At least one is
> still unresolved (stereo displays may be blank under unknown
> conditions).

It turned out that my hunch with regard to this particular bug was flat
wrong - the bug was an uninitialized value error that caused the camera
to slew left and right by an undefined (and typically very large) amount
when in stereo mode.  You could work around the bug by setting
display.stereodepth to some known value (like what the default should
have been: 0.0).

-Jonathan